replaceFirst method
Replaces the first occurrence of oldValue with newValue.
Example:
'hello hello'.replaceFirst('hello', 'hi'); // 'hi hello'
Implementation
String replaceFirst(String oldValue, String newValue) {
final index = indexOf(oldValue);
if (index == -1) return this;
return '${substring(0, index)}$newValue${substring(index + oldValue.length)}';
}